The present invention is directed to ratchet mechanisms of the type often used in ratcheting tools such as ratchet wrenches, ratchet screwdrivers, speed wrenches, and the like. This invention is specifically directed to a reversing ratchet mechanism which has both a simplified construction and increased mechanical strength. Thus, while the present invention is described as it directly relates to ratchet wrenches, it should be appreciated that the scope of the present invention encompasses the general field of ratcheting devices.
Ratcheting devices have been extensively developed in the past; however, the trend of such development has been to produce increasingly complicated ratchet mechanisms requiring a multiplicity of elements. While these complicated structures have accomplished the goal of functionality the increased complexity of the mechanisms has led to disadvantages. For example, as in any product, the increased complexity of the structure correspondingly increases production costs. These increased production costs result both from the cost of producing the specialized parts which make up the structure and in the increase of labor costs in assembling the device. Another disadvantage with complicated mechanisms is the risk of failure, especially where failure of a single element may result in failure of the device as a whole. Thus, with the increased number of parts, it raises the likelihood of a part failure that may result in major failure of the device. Finally, due to the size and complexity of parts, complicated ratcheting structures are more susceptible to contamination by dirt or other substances which can cause the mechanisms to jam or otherwise fail to perform.
The ratcheting structure according to the present invention is developed to simplify the construction of ratchet drives so that only a minimal number of parts are used in constructing the device. Since these parts are packaged in a standard sized wrench, each part can take on larger dimensions so as to increase the mechanical strength of the mechanism making the ratchet drive more durable and resistive to shear forces than the smaller parts of more complex mechanisms. The present invention accomplishes this greater strength by providing a sliding pawl member which slides across a slide surface. This pawl member is placed under compression forces against the slide surface. Prior art ratchet structures typically utilize relatively small pawl members or "dogs" which pivot between left and right drive positions on a pivot pin.
One example of such a pivot pawl structure is found in U.S. Pat. No. 4,147,076 issued Apr. 3, 1979 to Wright, et al. Likewise, U.S. Pat. No. 3,233,481 issued Feb. 8, 1966 to Bacon and U.S. Pat. No. 4,406,186 issued Sept. 27, 1983 to Gummow disclose ratchet mechanisms wherein the ratchet controlling pawl element is pivotally mounted on a pivot pin. Numerous other pivoting pawl structures are known in the prior art. The problem with these pivoting pawl structures, as noted above, is that the torque forces placed on the drive mechanism may cause a shearing of a pawl pivot pin or breakage of the pawl member thus causing a breakdown of the ratchet structure.
U.S. Pat. No. 3,044,591 issued July 17, 1962 to Kilness and U.S. Pat. No. 4,053,037 issued Oct. 11, 1977 to Solomon each disclose different structures wherein the pawl element pivots between left and right drive positions but is not constrained for pivotal motion about a pivot pin. Rather, the pawl member in these two patents floats on biasing elements which allow pivotal movement. U.S. Pat. No. 4,520,697 issued June 4, 1985 to Moetelli discloses a fairly complicated ratchet structure wherein a small ratcheting element slides along an arcuate surface portion of a drive member and is held in position by means of a biasing spring or pin which moves along with and controls movement of the pawl element. Due to its construction, this pawl element is of extremely small size so that only a small surface region of pawl element becomes engaged in the drive mode.